1. Field of the Invention
This invention relates to a buckle having a webbing gripping device. In particular, the invention relates to a buckle or other device having a gripping cam that grips a strap or length of webbing and prevents the it from slipping.
2. The Prior Art
Many types of buckles are used to secure two ends of a strap or length of webbing together, typically for use as safety belts, or in luggage or outerwear. Typically, these buckles have a series of transverse arms through which the strap is threaded. These arms allow the webbing to be adjusted to fit the size of the user. When tension is applied by the strap, the strap tends to stay in place due to the friction of the strap against itself and the buckle. However, if the tension is applied perpendicular to the buckle, the friction on the strap is reduced and it can easily slide out of the buckle.
This phenomenon occurs frequently when the buckle is used as a child restraining belt in such places as high chairs. Because an infant has a very small circumference, the angle at which the tension is applied to the buckle is rarely near 180.degree., and can often approach 90.degree.. At this point, the strap can easily slide out of the buckle and the belt is rendered ineffectual. Agitated motion by the infant while strapped into the belt can further increase the risk of slippage.
Accordingly, there have been efforts to provide a device that securely grips the strap or webbing under tension from all angles. One such device is shown in U.S. Pat. No. 5,651,166 to Lundstedt. This device has a flexible projecting member that rests against a transverse member of the buckle. The webbing is threaded in between the projecting member and the transverse member, and the tension from the projecting member keeps the webbing in place. This device has the disadvantage that once the webbing is sufficiently tightened, it cannot be easily loosened from the buckle to enlarge the belt.
U.S. Pat. No. 4,567,628 to Prete, Jr. et al. shows a buckle assembly having a webbing gripping device in the form of a cam member that firmly holds the webbing against the buckle. This device is useful as long as the cam member is functional. However, due to the tensioned arrangement of the cam member, there is a great risk that the cam member may break during use, causing the webbing to be completely released from the buckle.
Another device produced by Yoshida Kogyo K.K. (YKK) utilizes a pivoting grooved arm that grips the webbing as it is pulled tight against the buckle. The arm is a separate piece that is loosely held between the two sides of the buckle. While this device is easily adjustable, the webbing can easily slip out of the buckle if the tension is applied perpendicular to the buckle, as described above.